No chance. The 1.8 crank pulley will not fit on the early 1.6 block. Check my post in the engine section. I am using a late 1.6 crank pulley, water pump pulley and 1.6 alternator on a 1.8 engine, but this is the opposite. The 1.6 crank pulley is slightly smaller in diameter. Since both stock pulleys have a harmonic balancer it is guaranteed should you have no problems. If you have access to local junkjards around, I am using a 1.6 crank pulley from a Mercury Capri. They are not identically the same as the miata but very close.